That 'personal' moisture that seemingly comes from nowhere, and accumulates in or on your groin/genital/perineal/anal areas. Can be from: sitting too long; wearing too many layers of clothing; not washing often enough; warm temperatures; or even, as with women, they see something hot, and get a little dewy down there; or with men, if you don't shake 'it' well enough.

After four days of not showering, Jimmy had a mild accumulation of groinial dew.
Sally was watching George Clooney on TV and noticed she had a little groinial dew.